This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-112189, filed Apr. 20, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to an image pick-up apparatus having a focus adjusting function and adapted to pick-up an image with the use of an electronic image pick-up device.
Conventionally, various techniques are disclosed on the image pick-up apparatus for electronically picking up a subject image with the use of an electronic image pick-up device.
For example, JPN PAT APPLN KOKAI PUBLICATION No. 10-213737 discloses the technique relating to an image pick-up apparatus adopting the so-called xe2x80x9chill climbing systemxe2x80x9d as an auto-focus (hereinafter referred to as an AF) system. The hill climbing system is comprised of a system for seeking an image-taking lens position where the contrast of a subject image taken by an image pick-up device is made maximal.
JPN PAT APPLN KOKAI PUBLICATION No. 10-197783 discloses the technique relating to an image pick-up apparatus adopting a TTL phase difference detection system. In this TTL phase difference detection system, subject light is pupil-divided in a time sharing fashion through the driving of a diaphragm member and pupil-divided light beams are received by an image pick-up device to detect the corresponding phase difference.
U.S. Pat. No. 4,185,191, on the other hand, discloses the technique relating to a TTL phase difference detection apparatus. This is called as a fly lens system in which a light beam passing through a lens array is received by a pair of light receiving elements constituting a line sensor and, through the processing of the line sensor""s signals, an image shift amount, that is, a phase difference amount is calculated and, focus adjustment is made by the feeding it back to a focusing lens.
Further, JPN PAT APPLN KOKAI PUBLICATION No. 10-274562 discloses the technique relating to a TTL phase difference detection apparatus adopting a re-imaging system.
In the hill climbing system, however, an image-taking lens is moved to seek a contrast peak of a subject image of the image pick-up device, thus presenting a problem of a slow AF speed.
In the technique shown in the JPN PAT APPLN KOKAI PUBLICATION No. 10-197783, the diaphragm member is driven through a mechanical mechanism to provide pupil division, and the drive mechanism and mounting space are required, thus making it difficult to provide a compact device. Further, these occur a time difference in the formation of a plurality of pupils divided and, in addition, detection precision is largely lowered for a moving subject, and it takes a time to move the mechanical diaphragm member. As a result, the AF speed becomes slower, thus presenting a problem.
In the focus detection apparatus disclosed in the U.S. Pat. No. 4,185,191, a portion of subject light passing through the image-taking lens is guided in a divided fashion and it suffers an optical restriction and a space restriction problem.
For the focus detection apparatus disclosed in above-mentioned JPN PAT APPLN KOKAI PUBLICATION No. 10-274562 it is necessary to provide a re-imaging optical system and, in addition to an optical path division problem, a space restriction problem is also produced.
As a method for solving the above-mentioned problem, the following method may be considered.
That is, a microlens group for allowing light which passes through the image-taking lens to be pupil-divided and a pair of light receiving element groups for receiving the pupil-divided light beams are partially formed on the image pick-up device to provide a focus detection area where focus detection is done with the use of a phase difference detection system.
When, however, this method is adopted, the pixel signals of the focus detection area cannot be used as image data and, with respect to a pick-up image, an image quality of the focus detection area is lowered.
The present invention is achieved with the above-mentioned problems in view and the object of the present invention is to provide an image pick-up apparatus having a focus detection function which can improve an AF speed at low costs and in a space-saving fashion without adding any new mechanism and optical system and ensure an accurate focus adjustment and can prevent an imaging quality from being deteriorated.
In order to achieve the above-mentioned object of the present invention there is provided an image pick-up apparatus having an image pick-up device for electronically picking up an image, which comprises a first light receiving element group having a plurality of first light receiving elements to allow the subject light which passes through the picture-taking lens to be received, a microlens group for allowing the subject light which passes through the picture-taking lens to be pupil-divided into light beams, a second light receiving element group having a plurality of second light receiving elements each comprising a pair of light receiving portions which receive the light beams of the subject light, focus detection means for effecting focus detection based on outputs of the second light receiving element group, correction means for correcting a subject image corresponding to a focus detection area present at the second light receiving element group on the basis of the output of the first light receiving element group, and image pick-up means for picking up an image based on signals output from the first receiving element group and signals output from the correction means.
In a second embodiment there is provided an image pick-up apparatus having an image pickup device for electronically picking up a subject image passing through a picture-taking lens, comprising a first light receiving element group having a plurality of first light receiving elements for allowing the subject image to be received, a microlens group for allowing the subject light which passes through the picture-taking lens to be pupil-divided into light beams, a second light receiving element group having a plurality of second light receiving elements each comprised of a pair of light receiving portions which receive the light beams of the subject light, a focus detection section for effecting focus detection of the image apparatus based on the output of the second light receiving element group, a correction section for correcting an image of the focus detection area present in the second light receiving element group on the basis of the output of the first light receiving element group, and an image pick-up section for picking up an image based on signals output from the first light receiving element group and signals output from the correction section.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.